Hand-arm vibration syndrome with use of anti-vibration chain saws: 19-year follow-up study of forestry workers

Work-related and personal factors in shoulder disorders among electronics workers: findings from an electronics enterprise in Taiwan

BACKGROUND

The electronics industry is one of the largest global industries, and significant numbers of workers are engaged in this industry. Evidence suggests two associations, including one between ergonomic risks and shoulder disorders and another between psychological stress and psychological problems among workers in this industry. Investigations on ergonomic risks, psychological stress, and sex effects for shoulder disorders in this industry are limited. This study aimed to explore personal and work-related factors associated with shoulder disorders and to investigate the combined effect of similar ergonomic risk factors.

METHODS

In this cross-sectional study, 931 workers aged 20 to 58 from an electronics factory in Taiwan were recruited. A Nordic musculoskeletal questionnaire was used to assess shoulder symptoms. Sociodemographic factors and work-related factors, including psychological stress, were assessed. One hundred random sample workers with shoulder symptoms underwent a standardized clinical test for the evaluation of subacromial impingement syndrome. The ergonomic risks were assessed by the risk filter of 'upper limb disorders in the workplace', including repetition, posture, force, vibration, and duration of exposure.

RESULTS

The prevalence of shoulder symptoms was 30.5, and 19% of those with shoulder symptoms had subacromial impingement syndrome. In multivariable analyses, older age (adjusted odds ratio (aOR) = 1.37, 95% CI 1.01-1.86), repetition (aOR = 1.73, 95% CI 1.15-2.60) and posture (aOR = 1.85, 95% CI 1.10-3.11) were associated with shoulder symptoms. Regarding the gender effect, older age (aOR = 1.46, 95% CI 1.01-2.11), repetition (aOR = 1.64, 95% CI 1.00-2.68), posture (aOR = 1.89, 95% CI 1.01-3.52), and force (aOR = 1.68, 95% CI 0.99-2.85) were associated with shoulder symptoms in men, whereas posture (aOR = 2.12, 95% CI 0.99-4.57) was associated with symptoms in women.

CONCLUSIONS

This study implies that repetition and posture are important risk factors for shoulder disorders in the electronics industry. The risk exhibited sex differences, and force was more important for shoulder disorders in men. Such information is useful to help occupational health practitioners and policy makers conduct preventive programmes on shoulder disorders in this working population. Future longitudinal studies on work-related shoulder disorders are warranted.

Musculoskeletal complications of hand-arm vibration syndrome among tyre shop workers in Kelantan, Malaysia

Objectives. Exposure to hand-arm vibration (HAV) is associated with hand-arm vascular syndrome (HAVS), which is characterized by musculoskeletal complications. However, evidence on this matter has been inconclusive. Therefore, this study aimed to determine and compare the prevalence of musculoskeletal complications of HAVS between a high-exposure (≥5 m·s^-2) group and a low-moderate-exposure (<5 m·s^-2) group and to explore the factors associated with the musculoskeletal complications of HAVS among tyre shop workers in Kelantan, Malaysia. Methods. A cross-sectional study involving 200 tyre shop workers was carried out. HAV was measured by a vibration meter. The workers were divided into two exposure groups - according to their 8-h time-weighted average, A(8), of vibration exposure - and compared. Results. Almost half of the workers reported musculoskeletal complications of the upper limbs and neck. Only the lifetime vibration dose (LVD) was significantly associated with the development of musculoskeletal complications. Conclusion. The high-exposure group had a higher prevalence of musculoskeletal complications. Only the LVD was significantly associated with complications. However, all factors of the work system, such as ergonomics, handgrip force and posture, might contribute to the development of musculoskeletal complications of HAVS and should be included in assessments.

Dose-Response Relationship between Physical Workload and Specific Shoulder Diseases-A Systematic Review with Meta-Analysis

Several epidemiological studies have found an association between shoulder-loaded work activities and specific shoulder diseases. No study has derived the dose-response relationship and resulting doubling dose, important for the recognition of occupational diseases. This systematic review is an update of the van der Molen et al. (2017) review. Based on its methodologies, we identified new studies published up to November 2018. The dose-response relationship between physical occupational demands (hands at/above shoulder level, repetitive movements, forceful work, hand-arm vibrations) and specific shoulder diseases (defined as ICD-10 M 75.1-5: rotator cuff syndrome, bicipital tendinitis, calcific tendinitis, impingement, and bursitis) was derived. No evidence for sex-specific differences in the dose-response relationship was found. If there were at least two studies with comparable exposures, a meta-analysis was carried out. The pooled analysis resulted in a 21% risk increase (95% CI 4–41%) per 1000 h of work with hands above shoulder level. A meta-analysis was not possible for other occupational burdens due to the low number of studies and differing exposure measurements; an estimate of the doubling dose was made based on the cohort study of Dalbøge et al. (2014). To conclude, the present systematic review with meta-analysis contributes to knowledge of the level of exposure at which specific shoulder diseases—particularly rotator cuff lesions—should be recognized as an occupational disease.

Vascular component of hand-arm vibration syndrome: a 22-year follow-up study

BACKGROUND

Vibration-induced white finger (VWF) is often assessed using the Stockholm Workshop Scale (SWS) and cold challenge plethysmography. However, long-term longitudinal studies using both methods are scarce.

AIMS

To study the long-term course and prognostic factors of VWF assessed with the SWS and photoplethysmography (PPG), and to examine the effects of lifestyle on PPG score, regardless of VWF status.

METHODS

Forty male construction workers were examined with a test battery and clinical examination in 1994 and 2016/17.

RESULTS

At baseline, the sample comprised 27 workers with, and 13 without, symptoms of hand-arm vibration syndrome (HAVS). Thirty-five workers reported vibration exposure during follow-up. The mean age of the workers was 60 years (45-78) at follow-up. The paired t-test showed that PPG scores deteriorated from 1994 to 2017 in the 27 workers with HAVS in 1994 (mean difference 2.7 min, 95% confidence interval (CI) 0.2-5.2). However, there was no statistically significant change in SWS scores in these workers over time. Smoking and age were associated with PPG score deterioration. Vibration exposure during follow-up predicted SWS score deterioration: 1000 h of exposure predicted a deterioration stage of 0.09 (95% CI 0.03-0.16). Analysis of all 40 workers showed that 2017 PPG scores were associated with positive serum cotinine and self-reported smoking during follow-up.

CONCLUSIONS

Whereas age and smoking predicted a PPG deterioration, continued vibration exposure predicted worsening of white finger symptoms. The association of PPG score and smoking should be considered in diagnostic and prognostic factor evaluations.

Risk of subacromial shoulder disorder in airport baggage handlers: combining duration and intensity of musculoskeletal shoulder loads

Musculoskeletal shoulder load among baggage handlers measured by combining duration and intensity based on biomechanical and epidemiological information may be a stronger predictor of subacromial shoulder disorders than baggage handler seniority. In 2012, a cohort of baggage handlers employed at Copenhagen Airport in 1990-2012, and a cohort of unskilled otherwise employed men answered a survey. Self-reported information on work tasks during employment in the airport in combination with work task specific biomechanically modelled forces in the shoulder joint was used to estimate shoulder load. Exposure measures were accumulated shoulder abduction moment, accumulated shoulder compression force, accumulated supraspinatus force and baggage handler seniority. The outcome was subacromial shoulder disorder registered in the Danish National Patient Register. When analyses were adjusted by all confounders except age, exposure variables showed close to significant associations with subacromial shoulder disorder. Results could not confirm our hypothesis that combined information on work task duration and shoulder load intensity was stronger associated with subacromial shoulder disorder than seniority. Practitioner Summary: In this study we sought to identify if the exposure to work-related musculoskeletal shoulder loading including duration and intensity among baggage handlers was associated with subacromial shoulder disorder. We found that there was an association but this was not stronger than that between baggage handler seniority and subacromial shoulder disorder.

Vibration and Ergonomic Exposures Associated With Musculoskeletal Disorders of the Shoulder and Neck

Background

According to the US Bureau of Labor Statistics, musculoskeletal disorders (MSDs) accounted for 32% of all nonfatal injury and illness cases in 2014 among full-time workers. Our objective was to review and summarize the evidence linking occupational exposures to vibration and awkward posture with MSDs of the shoulder and neck.

Methods

A literature search was conducted using the terms musculoskeletal disorders, vibration, and awkward posture. All types of observational epidemiologic studies, with the exception of case reports, published during 1998–2015 were included. Databases searched were MEDLINE (Ovid), Embase (Ovid), Scopus, Ergonomic Abstracts, NIOSHTIC-2, and Health and Safety Science Abstracts.

Results

Occupational exposures to whole-body or hand–arm vibration were significantly associated with or resulted in MSDs of the shoulder and neck. Awkward postures while working were also associated with MSDs in these locations. These findings were consistent across study designs, populations, and countries.

Conclusion

Occupational exposure to vibration and awkward posture are associated with shoulder and neck MSDs. Longitudinal studies are required to elucidate the mechanisms responsible for these associations, and intervention studies are warranted.

Work-related risk factors for specific shoulder disorders: a systematic review and meta-analysis

The objective of this systematic review and meta-analysis is to examine which work-related risk factors are associated with specific soft tissue shoulder disorders. We searched the electronic databases of Medline and Embase for articles published between 2009 and 24 March 2016 and included the references of a systematic review performed for the period before 2009. Primary cross-sectional and longitudinal studies were included when outcome data were described in terms of clinically assessed soft tissue shoulder disorders and at least two levels of work-related exposure were mentioned (exposed vs less or non-exposed). Two authors independently selected studies, extracted data and assessed study quality. For longitudinal studies, we performed meta-analyses and used GRADE (Grades of Recommendations, Assessment, Development and Evaluation) to assess the evidence for the associations between risk factors and the onset of shoulder disorders. Twenty-seven studies met the inclusion criteria. In total, 16 300 patients with specific soft tissue shoulder disorders from a population of 2 413 722 workers from Denmark, Finland, France, Germany and Poland were included in the meta-analysis of one case-control and six prospective cohort studies. This meta-analysis revealed moderate evidence for associations between shoulder disorders and arm-hand elevation (OR=1.9, 95% CI 1.47 to 2.47) and shoulder load (OR=2.0, 95% CI 1.90 to 2.10) and low to very low evidence for hand force exertion (OR=1.5, 95% CI 1.25 to 1.87), hand-arm vibration (OR=1.3, 95% CI 1.01 to 1.77), psychosocial job demands (OR=1.1, 95% CI 1.01 to 1.25) and working together with temporary workers (OR=2.2, 95% CI 1.2 to 4.2). Low-quality evidence for no associations was found for arm repetition, social support, decision latitude, job control and job security. Moderate evidence was found that arm-hand elevation and shoulder load double the risk of specific shoulder disorders. Low to very-low-quality evidence was found for an association between hand force exertion, hand-arm vibration, psychosocial job demands and working together with temporary workers and the incidence of specific shoulder disorders.

Subacromial shoulder disorders among baggage handlers: an observational cohort study

PURPOSE

To assess the influence of cumulative employment as baggage handler on the risk of incident subacromial shoulder disorders. Baggage handling is characterized by repetitive work primarily consisting of heavy lifting in awkward positions and time pressure.

METHODS

This cohort study is based on the Copenhagen Airport Cohort consisting of unskilled men with employment at Copenhagen Airport and unskilled men with employment in other firms in the Greater Copenhagen area during the period 1990-2012. Only men were included. We followed the cohort in the National Patient Register and Civil Registration System. The primary exposure was cumulative years of employment as a baggage handler, and the primary outcome was diagnoses and surgical treatment of subacromial shoulder disorders.

RESULTS

The cohort contained 3396 baggage handlers and 63,909 workers in the reference group. Baggage handlers with longer cumulative years of employment had higher incidence compared to baggage handlers with shorter employment; for example, baggage handlers with 10-19 years of employment had incidence rate ratio of 2.07 (95 % confidence interval, 1.27-3.38) compared to baggage handlers with less than 3 years of employment. Spline regression showed an increase in incidence within the first few years after employment whereupon the increased risk remained constant for longer employment. Baggage handlers had increased incidence in younger ages than the reference population.

CONCLUSIONS

In this large cohort study, we found increased incidence of subacromial shoulder disorders for workers with longer cumulative years of employment. These results support that long-term lifting in awkward positions and time pressure influences the risk of subacromial shoulder disorders.

Safety and severity of accelerations delivered from whole body vibration exercise devices to standing adults

OBJECTIVES

Whole body vibration devices are used as a means to augment training, and their potential to treat a range of musculoskeletal diseases and injuries is now being considered. The goal of this work is to determine the degree to which acceleration delivered by whole body vibration devices at the plantar surfaces of a standing human is transmitted through the axial and appendicular skeleton, and how this mechanical challenge corresponds to the safety threshold limit values established by the International Standards Organization ISO-2631.

DESIGN

Non-blinded laboratory assessment of a range of whole body vibration devices as it pertains to acceleration transmission to healthy volunteers.

METHODS

Using skin and bite-bar mounted accelerometers, transmissibility to the tibia and cranium was determined in six healthy adults standing on a programmable whole body vibration device as a function of frequency and intensity. Measures of transmissibility were then made from three distinct types of whole body vibration platforms, which delivered a 50-fold range of peak-to-peak acceleration intensities (0.3-15.1 gp-p; where 1g is Earth's gravitational field).

RESULTS

For a given frequency, transmissibility was independent of intensity when below 1g. Transmissibility declined non-linearly with increasing frequency. Depending on the whole body vibration device, vibration ranged from levels considered safe by ISO-2631 for up to 8h each day (0.3 gp-p @ 30 Hz), to levels that were seven times higher than what is considered a safe threshold for even 1 min of exposure each day (15.1 gp-p @ 30 Hz). Transmissibility to the cranium was markedly attenuated by the degree of flexion in the knees.

CONCLUSIONS

Vibration can have adverse effects on a number of physiologic systems. This work indicates that readily accessible whole body vibration devices markedly exceed ISO guidelines for safety, and extreme caution must be practiced when considering their use.

A case report of vibration-induced hand comorbidities in a postwoman

Background

Prolonged exposure to hand-transmitted vibration is associated with an increased occurrence of symptoms and signs of disorders in the vascular, neurological and osteoarticular systems of the upper limbs. However, the available epidemiological evidence is derived from studies on high vibration levels caused by vibratory tools, whereas little is known about possible upper limb disorders caused by chronic exposure to low vibration levels emitted by fixed sources.

Case presentation

We present the case of a postwoman who delivered mail for 15 years using a low-powered motorcycle. The woman was in good health until 2002, when she was diagnosed with bilateral Raynaud's phenomenon. In March 2003 a bilateral carpal tunnel syndrome was electromyographically diagnosed; surgical treatment was ineffective. Further examinations in 2005 highlighted the presence of chronic tendonitis (right middle finger flexor).

Risk assessment

From 1987, for 15 years, our patient rode her motorcycle for 4 h/day, carrying a load of 20-30 kg. For about a quarter of the time she drove over country roads. Using the information collected about the tasks carried out every day by the postwoman and some measurements performed on both handles of the motorcycle, as well as on both iron parts of the handlebars, we reconstructed the woman's previous exposure to hand-arm vibration. 8-hour energy-equivalent frequency weighted acceleration was about 2.4 m/s². The lifetime dose was 1.5 × 10⁹(m²/s⁴)hd.

Conclusions

The particular set of comorbidities presented by our patient suggests a common pathophysiological basis for all the diseases. Considering the level of exposure to vibrations and the lack of specific knowledge on the effects of vibration in women, we hypothesize an association between the work exposure and the onset of the diseases.

Quantitative test for sensory hand symptoms based on mechanoreceptor-specific vibrotactile thresholds

A vibrotactile test for assessing the presence or absence of sensory symptoms in the hand has been developed from thresholds believed mediated by Merkel disks and Meissner corpuscles at the fingertips. It is constructed from the summed differences between the thresholds recorded at the fingertip of an individual and the mean values of the threshold for healthy persons at the same stimulation frequencies. The summed normalized threshold shift, TS(Sum(SD)), is shown to be related to reports by subjects of numbness and pain using three statistical tests for evaluating the significance of associations in 2x2 contingency tables. The small number of subjects (15) restricts direct calculation of a fence value for TS(Sum(SD)), t, between the presence and absence of symptoms: accordingly, interpolation between calculated t values has been performed graphically. A common range of t values can be identified that is judged significantly by each statistical test (3.3<or=t<3.9 for numbness; 3.6<or=t<4.1 for pain). The range encompasses the boundary previously identified between "normal" and "abnormal" vibrotactile thresholds, that is, thresholds for which the (two-sided) probability of occurrence in the hands of healthy persons is p approximately 0.05.

Dose-response relationship between exposure to hand-arm vibration and health effects among metalworkers

OBJECTIVES

The aim of this study was to explore the relationship of exposure to hand-arm vibration (HAV) and vascular, sensorineural and musculoskeletal symptoms and symptoms of carpal tunnel syndrome (CTS) in a population of Finnish metalworkers.

METHODS

A questionnaire on HAV exposure and symptoms was sent to 530 metalworkers. Those who reported finger blanching, numbness or tingling of the fingers or symptoms of CTS were invited to further examinations (n = 133). Their cumulative lifelong exposure to HAV, the level of current exposure and the history of use of tools causing impulse vibration were evaluated. The association of different symptoms with the HAV exposure was assessed with logistic regression analyses adjusted for age and smoking. The vibration perception thresholds (VPTs) were tested according to ISO 13091-1:2001.

RESULTS

The cumulative exposure index varied between 0 and 115,000 m(2) years d s(-4), the mean being 20,591 m(2) years d s(-4). The average of current daily vibration exposure was 1.6 m s(-2) and 39% of the participants had a history of exposure to impulse vibration. Of the respondents, 49% reported white fingers, 66% neurosensory symptoms, 56% symptoms of CTS and 75% musculoskeletal symptoms. The cumulative exposure index was associated with symptoms of white fingers [odds ratio (OR) 2.4-4.5], with symptoms of CTS (OR 4.6-6.1), with neurosensory symptoms (OR 5.7-17.3) and with musculoskeletal symptoms (OR 4.7-5.4). The risk of all these symptoms increased as the cumulative vibration dose increased. The history of exposure to impulse vibration had a significant effect on the occurrence of neurosensory symptoms (P = 0.024). The current exposure to HAV correlated significantly with all of the above-mentioned symptoms. The results of the VPT test were associated with the level of cumulative exposure to HAV.

CONCLUSIONS

There seems to be a dose-response relationship between the cumulative lifetime vibration dose of the HAV and finger blanching, sensorineural symptoms, symptoms of CTS and musculoskeletal symptoms of upper limbs and neck in the group of metalworkers of the study. The risk for neurosensory symptoms was the most significantly related to exposure to HAV and also to impulse vibration. Further studies are needed to confirm the present results also in other occupational groups taking into account the possible synergistic effect of workload as well.

Application of metrics constructed from vibrotactile thresholds to the assessment of tactile sensory changes in the hands

Two tools for assessing tactile sensory disturbances in the hands have been constructed from mechanoreceptor-specific vibrotactile threshold shifts, and thresholds changes with time, and employed in a prospective study of forest workers (N=18). Statistically significant positive threshold shifts (i.e., reductions in sensitivity compared to the hands of healthy persons) were found in five hands at study inception (13.9%), and 15 hands at follow-up (41.7%). Four patterns of threshold shift could be identified, involving selectively the median and/or ulnar nerve pathways and/or end organs. Statistically significant positive threshold changes (i.e., reductions in sensitivity with time) were recorded in 69.4% of the hands over a five-year period, even though a majority of the workers remained symptom free. If the thresholds recorded from subjects not working with power tools are used to control for aging, lifestyle, and environmental factors during the five year period, then 40% of the remaining subjects are found to be experiencing work-related threshold changes in their hands. The ability of the threshold shift metric to predict the numbness reported by these subjects shows that it is closely associated with the tactile sensory changes occurring in their hands.

A follow up study of vascular disorders in vibration-exposed forestry workers

OBJECTIVES

To investigate the occurrence of vibration-induced white finger (VWF) and the cold response of digital arteries in a group of forestry workers, most of whom had used anti-vibration (AV) chain saws solely.

METHODS

One hundred and twenty-eight forestry workers underwent initially a medical examination and a standardized cold test with measurement of the change in finger systolic blood pressure after finger cooling from 30 to 10 degrees C (FSBP%(10 degrees )). They were re-examined two or three times over the calendar period 1990-1999. Seventy-one forestry workers were active over the entire follow up period, while 57 retired after 1-8 years from the initial investigation.

RESULTS

The initial prevalence and the cumulative incidence of VWF over the follow up period were 26.6 and 11.7%, respectively. In the retired workers, the new cases of VWF occurred before their retirement, that is when they were still active. There were no significant changes in FSBP%(10 degrees ) in the active forestry workers over the follow up period. A significant increased in FSBP%(10 degrees ) (i.e. improvement) was observed in the retired workers at the end of the follow up. FSBP%(10 degrees ) at the cross-sectional investigation was significantly lower in the forestry workers who developed VWF during the follow up than in those who never experienced finger blanching over the study period.

CONCLUSION

The findings of this follow up study suggest that forestry workers with work experience limited to AV chain saws are still at risk of developing VWF. Cessation of vibration exposure in the retired workers was associated with a beneficial effect on the cold response of digital arteries. Cold-induced digital arterial hyperresponsiveness at the initial investigation was a predictive factor for the onset of VWF over time.

The Hand-Arm Vibration International Consortium (HAVIC): Prospective Studies on the Relationship Between Power Tool Exposure and Health Effects

OBJECTIVES

The Hand-Arm Vibration International Consortium (HAVIC) is a collaboration of investigators from Europe and North America studying health effects from hand-arm vibration (HAV). Features include prospective design, cross-cohort exposure, and health assessment methods.

METHODS

Two new cohorts (dental hygienists and dental hygiene students), two existing cohorts (Finnish forest workers, and Swedish truck cab assemblers), and a previous population (US shipyard workers) are included. Instruments include surveys, quantitative medical tests, physical examination, and work simulation and data logging to assess exposure. New methods were developed for nerve conduction and data logging.

RESULTS

Findings on the relationship between nerve conduction and skin temperature in HAV-exposed subjects resulted in a new approach to subject warming.

CONCLUSIONS

Integrating established cohorts has advantages over de novo cohort construction. Complex laboratory tests can be successfully adapted for field use.

Method for detecting small changes in vibrotactile perception threshold related to tactile acuity

Two metrics, expressing the change in mechanoreceptor-specific vibrotactile thresholds at a fingertip over a time interval of months or years, and the shift in threshold from the mean values recorded from the fingertips of healthy persons, have been constructed for thresholds measured from individual fingers. The metrics assume the applicability of the acute adaptation property of mechanoreceptors, which has been confirmed by thresholds obtained from 18 forest workers on two occasions, separated by 5 years. Hence, when expressed in decibels, both threshold changes and threshold shifts may be averaged at frequencies mediated by the same receptor population to improve precision. Differences between threshold changes at frequencies mediated by the same receptor population may be used to identify inconsistent subject performance, and hence potentially erroneous results. For this group of subjects, the threshold changes and threshold shifts at frequencies believed mediated by the slowly adapting type I (SAI) (4 and 6.3 Hz) and rapidly adapting type I (FAI) (20 and 32 Hz) receptors within each finger were correlated. In these circumstances, which may be expected to occur for some work-induced and systemic peripheral neuropathies, both threshold changes and threshold shifts may be summed over SAI and FAI receptors to improve precision, and hence the potential for interpretation.